System and method for supporting router sma abstractions for smp connectivity checks across virtual router ports in a high performance computing environment

ABSTRACT

Systems and methods for supporting SMP connectivity checks across virtual router in a high performance computing environment. In accordance with an embodiment, SMA model enhancements allow for the possibility to send a packet (i.e., SMP) that is addressed to a local router port. The SMA where the packet is addressed can receive the packet, and then apply a new attribute that defines that the requested information is on a remote node (e.g., connected by a physical link across subnets). In accordance with an embodiment, the SMA can operate as a proxy (receives a SMP and sends another request), or the SMA can modify the original packet and send it on as an inter-subnet packet.

CLAIM OF PRIORITY AND CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to U.S. ProvisionalPatent Application entitled “SYSTEM AND METHOD FOR USING MULTIPLE LIDSPER VIRTUAL ROUTER PORT IN ORDER TO UTILIZE SWITCH LFT BASED FORWARDINGFOR BOTH LOCAL ROUTER PORT AND REMOTE TRAFFIC”, Application No.62/287,720, filed on Jan. 27, 2016, which is incorporated by referenceit its entirety.

COPYRIGHT NOTICE

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserves all copyrightrights whatsoever.

FIELD OF INVENTION

The present invention is generally related to computer systems, and isparticularly related to supporting SMA abstractions for SMP connectivitychecks across dual-port virtual router ports in a high performancecomputing environment.

BACKGROUND

As larger cloud computing architectures are introduced, the performanceand administrative bottlenecks associated with the traditional networkand storage have become a significant problem. There has been anincreased interest in using high performance lossless interconnects suchas InfiniBand (IB) technology as the foundation for a cloud computingfabric. This is the general area that embodiments of the invention areintended to address.

SUMMARY

Described herein are systems methods for supporting SMP connectivitychecks across virtual router ports in a high performance computingenvironment. An exemplary method can provide, at one or more computers,including one or more microprocessors, a first subnet, the first subnetcomprising a plurality of switches, the plurality of switches comprisingat least a leaf switch, wherein each of the plurality of switchescomprise a plurality of switch ports, a plurality of host channeladapters, each host channel adapter comprising at least one host channeladapter port, a plurality of end nodes, wherein each of the end nodesare associated with at least one host channel adapter of the pluralityof host channel adapters, and a subnet manager, the subnet managerrunning on one of the plurality of switches and the plurality of hostchannel adapters. The method can configure a switch port of theplurality of switch ports on a switch of the plurality of switches as arouter port. The method can logically connect the switch port configuredas the router port to a virtual router, the virtual router comprising atleast two virtual router ports. The method can send, by the subnetmanager, to the switch port of the plurality of switch ports on theswitch of the plurality of switches configured as the router port arequest packet addressed to the router port, wherein the request packetrequests connectivity information beyond the router port. Finally, themethod can modify, by a subnet management agent residing on the switchof the plurality of switches, the request packet.

In accordance with an embodiment, one or more of the plurality of hostchannel adapters (either of the first or second subnet) can comprise atleast one virtual function, at least one virtual switch, and at leastone physical function. The plurality of end nodes (of the first orsecond subnet) can comprise physical hosts, virtual machines, or acombination of physical hosts and virtual machines, wherein the virtualmachines are associated with at least one virtual function.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows an illustration of an InfiniBand environment, in accordancewith an embodiment.

FIG. 2 shows an illustration of a partitioned cluster environment, inaccordance with an embodiment

FIG. 3 shows an illustration of a tree topology in a networkenvironment, in accordance with an embodiment.

FIG. 4 shows an exemplary shared port architecture, in accordance withan embodiment.

FIG. 5 shows an exemplary vSwitch architecture, in accordance with anembodiment.

FIG. 6 shows an exemplary vPort architecture, in accordance with anembodiment.

FIG. 7 shows an exemplary vSwitch architecture with prepopulated LIDs,in accordance with an embodiment.

FIG. 8 shows an exemplary vSwitch architecture with dynamic LIDassignment, in accordance with an embodiment.

FIG. 9 shows an exemplary vSwitch architecture with vSwitch with dynamicLID assignment and prepopulated LIDs, in accordance with an embodiment.

FIG. 10 shows an exemplary multi-subnet InfiniBand fabric, in accordancewith an embodiment.

FIG. 11 shows an interconnection between two subnets in a highperformance computing environment, in accordance with an embodiment.

FIG. 12 shows an interconnection between two subnets via a dual-portvirtual router configuration in a high performance computingenvironment, in accordance with an embodiment.

FIG. 13 shows a flowchart of a method for supporting dual-port virtualrouter in a high performance computing environment, in accordance withan embodiment.

FIG. 14 is a flow chart illustrating a DR routed VSMP packet, inaccordance with an embodiment.

FIG. 15 is a flow chart illustrating a response to a DR routed VSMPpacket, in accordance with an embodiment.

FIG. 16 is a flow chart illustrating a LID routed VSMP packet, inaccordance with an embodiment.

FIG. 17 is a flow chart illustrating a response to a LID routed VSMPpacket, in accordance with an embodiment.

DETAILED DESCRIPTION

The invention is illustrated, by way of example and not by way oflimitation, in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that referencesto “an” or “one” or “some” embodiment(s) in this disclosure are notnecessarily to the same embodiment, and such references mean at leastone. While specific implementations are discussed, it is understood thatthe specific implementations are provided for illustrative purposesonly. A person skilled in the relevant art will recognize that othercomponents and configurations may be used without departing from thescope and spirit of the invention.

Common reference numerals can be used to indicate like elementsthroughout the drawings and detailed description; therefore, referencenumerals used in a figure may or may not be referenced in the detaileddescription specific to such figure if the element is describedelsewhere.

Described herein are systems and methods to support SMP connectivitychecks across virtual router ports a high performance computingenvironment.

The following description of the invention uses an InfiniBand™ (IB)network as an example for a high performance network. Throughout thefollowing description, reference can be made to the InfiniBand™specification (also referred to variously as the InfiniBandspecification, IB specification, or the legacy IB specification). Suchreference is understood to refer to the InfiniBand® Trade AssociationArchitecture Specification, Volume 1, Version 1.3, released March, 2015,available at http://www.inifinibandta.org, which is herein incorporatedby reference in its entirety. It will be apparent to those skilled inthe art that other types of high performance networks can be usedwithout limitation. The following description also uses the fat-treetopology as an example for a fabric topology. It will be apparent tothose skilled in the art that other types of fabric topologies can beused without limitation.

To meet the demands of the cloud in the current era (e.g., Exascaleera), it is desirable for virtual machines to be able to utilize lowoverhead network communication paradigms such as Remote Direct MemoryAccess (RDMA). RDMA bypasses the OS stack and communicates directly withthe hardware, thus, pass-through technology like Single-Root I/OVirtualization (SR-IOV) network adapters can be used. In accordance withan embodiment, a virtual switch (vSwitch) SR-IOV architecture can beprovided for applicability in high performance lossless interconnectionnetworks. As network reconfiguration time is critical to makelive-migration a practical option, in addition to network architecture,a scalable and topology-agnostic dynamic reconfiguration mechanism canbe provided.

In accordance with an embodiment, and furthermore, routing strategiesfor virtualized environments using vSwitches can be provided, and anefficient routing algorithm for network topologies (e.g., Fat-Treetopologies) can be provided. The dynamic reconfiguration mechanism canbe further tuned to minimize imposed overhead in Fat-Trees.

In accordance with an embodiment of the invention, virtualization can bebeneficial to efficient resource utilization and elastic resourceallocation in cloud computing. Live migration makes it possible tooptimize resource usage by moving virtual machines (VMs) betweenphysical servers in an application transparent manner. Thus,virtualization can enable consolidation, on-demand provisioning ofresources, and elasticity through live migration.

InfiniBand™

InfiniBand™ (IB) is an open standard lossless network technologydeveloped by the InfiniBand™ Trade Association. The technology is basedon a serial point-to-point full-duplex interconnect that offers highthroughput and low latency communication, geared particularly towardshigh-performance computing (HPC) applications and datacenters.

The InfiniBand™ Architecture (IBA) supports a two-layer topologicaldivision. At the lower layer, IB networks are referred to as subnets,where a subnet can include a set of hosts interconnected using switchesand point-to-point links. At the higher level, an IB fabric constitutesone or more subnets, which can be interconnected using routers.

Within a subnet, hosts can be connected using switches andpoint-to-point links. Additionally, there can be a master managemententity, the subnet manager (SM), which resides on a designated device inthe subnet. The subnet manager is responsible for configuring,activating and maintaining the IB subnet. Additionally, the subnetmanager (SM) can be responsible for performing routing tablecalculations in an IB fabric. Here, for example, the routing of the IBnetwork aims at proper load balancing between all source and destinationpairs in the local subnet.

Through the subnet management interface, the subnet manager exchangescontrol packets, which are referred to as subnet management packets(SMPs), with subnet management agents (SMAs). The subnet managementagents reside on every IB subnet device. By using SMPs, the subnetmanager is able to discover the fabric, configure end nodes andswitches, and receive notifications from SMAs.

In accordance with an embodiment, intra-subnet routing in an IB networkcan be based on linear forwarding tables (LFTs) stored in the switches.The LFTs are calculated by the SM according to the routing mechanism inuse. In a subnet, Host Channel Adapter (HCA) ports on the end nodes andswitches are addressed using local identifiers (LIDs). Each entry in alinear forwarding table (LFT) consists of a destination LID (DLID) andan output port. Only one entry per LID in the table is supported. When apacket arrives at a switch, its output port is determined by looking upthe DLID in the forwarding table of the switch. The routing isdeterministic as packets take the same path in the network between agiven source-destination pair (LID pair).

Generally, all other subnet managers, excepting the master subnetmanager, act in standby mode for fault-tolerance. In a situation where amaster subnet manager fails, however, a new master subnet manager isnegotiated by the standby subnet managers. The master subnet manageralso performs periodic sweeps of the subnet to detect any topologychanges and reconfigure the network accordingly.

Furthermore, hosts and switches within a subnet can be addressed usinglocal identifiers (LIDs), and a single subnet can be limited to 49151unicast LIDs. Besides the LIDs, which are the local addresses that arevalid within a subnet, each IB device can have a 64-bit global uniqueidentifier (GUID). A GUID can be used to form a global identifier (GID),which is an IB layer three (L3) address.

The SM can calculate routing tables (i.e., the connections/routesbetween each pair of nodes within the subnet) at network initializationtime. Furthermore, the routing tables can be updated whenever thetopology changes, in order to ensure connectivity and optimalperformance. During normal operations, the SM can perform periodic lightsweeps of the network to check for topology changes. If a change isdiscovered during a light sweep or if a message (trap) signaling anetwork change is received by the SM, the SM can reconfigure the networkaccording to the discovered changes.

For example, the SM can reconfigure the network when the networktopology changes, such as when a link goes down, when a device is added,or when a link is removed. The reconfiguration steps can include thesteps performed during the network initialization. Furthermore, thereconfigurations can have a local scope that is limited to the subnets,in which the network changes occurred. Also, the segmenting of a largefabric with routers may limit the reconfiguration scope.

An example InfiniBand fabric is shown in FIG. 1, which shows anillustration of an InfiniBand environment 100, in accordance with anembodiment. In the example shown in FIG. 1, nodes A-E, 101-105, use theInfiniBand fabric, 120, to communicate, via the respective host channeladapters 111-115. In accordance with an embodiment, the various nodes,e.g., nodes A-E, 101-105, can be represented by various physicaldevices. In accordance with an embodiment, the various nodes, e.g.,nodes A-E, 101-105, can be represented by various virtual devices, suchas virtual machines.

Partitioning in InfiniBand

In accordance with an embodiment, IB networks can support partitioningas a security mechanism to provide for isolation of logical groups ofsystems sharing a network fabric. Each HCA port on a node in the fabriccan be a member of one or more partitions. Partition memberships aremanaged by a centralized partition manager, which can be part of the SM.The SM can configure partition membership information on each port as atable of 16-bit partition keys (P_Keys). The SM can also configureswitch and router ports with the partition enforcement tables containingP_Key information associated with the end-nodes that send or receivedata traffic through these ports. Additionally, in a general case,partition membership of a switch port can represent a union of allmembership indirectly associated with LIDs routed via the port in anegress (towards the link) direction.

In accordance with an embodiment, partitions are logical groups of portssuch that the members of a group can only communicate to other membersof the same logical group. At host channel adapters (HCAs) and switches,packets can be filtered using the partition membership information toenforce isolation. Packets with invalid partitioning information can bedropped as soon as the packets reaches an incoming port. In partitionedIB systems, partitions can be used to create tenant clusters. Withpartition enforcement in place, a node cannot communicate with othernodes that belong to a different tenant cluster. In this way, thesecurity of the system can be guaranteed even in the presence ofcompromised or malicious tenant nodes.

In accordance with an embodiment, for the communication between nodes,Queue Pairs (QPs) and End-to-End contexts (EECs) can be assigned to aparticular partition, except for the management Queue Pairs (QP0 andQP1). The P_Key information can then be added to every IB transportpacket sent. When a packet arrives at an HCA port or a switch, its P_Keyvalue can be validated against a table configured by the SM. If aninvalid P_Key value is found, the packet is discarded immediately. Inthis way, communication is allowed only between ports sharing apartition.

An example of IB partitions is shown in FIG. 2, which shows anillustration of a partitioned cluster environment, in accordance with anembodiment. In the example shown in FIG. 2, nodes A-E, 101-105, use theInfiniBand fabric, 120, to communicate, via the respective host channeladapters 111-115. The nodes A-E are arranged into partitions, namelypartition 1, 130, partition 2, 140, and partition 3, 150. Partition 1comprises node A 101 and node D 104. Partition 2 comprises node A 101,node B 102, and node C 103. Partition 3 comprises node C 103 and node E105. Because of the arrangement of the partitions, node D 104 and node E105 are not allowed to communicate as these nodes do not share apartition. Meanwhile, for example, node A 101 and node C 103 are allowedto communicate as these nodes are both members of partition 2, 140.

Virtual Machines in InfiniBand

During the last decade, the prospect of virtualized High PerformanceComputing (HPC) environments has improved considerably as CPU overheadhas been practically removed through hardware virtualization support;memory overhead has been significantly reduced by virtualizing theMemory Management Unit; storage overhead has been reduced by the use offast SAN storages or distributed networked file systems; and network I/Ooverhead has been reduced by the use of device passthrough techniqueslike Single Root Input/Output Virtualization (SR-IOV). It is nowpossible for clouds to accommodate virtual HPC (vHPC) clusters usinghigh performance interconnect solutions and deliver the necessaryperformance.

However, when coupled with lossless networks, such as InfiniBand (IB),certain cloud functionality, such as live migration of virtual machines(VMs), still remains an issue due to the complicated addressing androuting schemes used in these solutions. IB is an interconnectionnetwork technology offering high bandwidth and low latency, thus, isvery well suited for HPC and other communication intensive workloads.

The traditional approach for connecting IB devices to VMs is byutilizing SR-IOV with direct assignment. However, achieving livemigration of VMs assigned with IB Host Channel Adapters (HCAs) usingSR-IOV has proved to be challenging. Each IB connected node has threedifferent addresses: LID, GUID, and GID. When a live migration happens,one or more of these addresses change. Other nodes communicating withthe VM-in-migration can lose connectivity. When this happens, the lostconnection can be attempted to be renewed by locating the virtualmachine's new address to reconnect to by sending Subnet Administration(SA) path record queries to the IB Subnet Manager (SM).

IB uses three different types of addresses. A first type of address isthe 16 bits Local Identifier (LID). At least one unique LID is assignedto each HCA port and each switch by the SM. The LIDs are used to routetraffic within a subnet. Since the LID is 16 bits long, 65536 uniqueaddress combinations can be made, of which only 49151 (0x0001-0xBFFF)can be used as unicast addresses. Consequently, the number of availableunicast addresses defines the maximum size of an IB subnet. A secondtype of address is the 64 bits Global Unique Identifier (GUID) assignedby the manufacturer to each device (e.g. HCAs and switches) and each HCAport. The SM may assign additional subnet unique GUIDs to an HCA port,which is useful when SR-IOV is used. A third type of address is the 128bits Global Identifier (GID). The GID is a valid IPv6 unicast address,and at least one is assigned to each HCA port. The GID is formed bycombining a globally unique 64 bits prefix assigned by the fabricadministrator, and the GUID address of each HCA port.

Fat-Tree (FTree) Topolodies and Routing

In accordance with an embodiment, some of the IB based HPC systemsemploy a fat-tree topology to take advantage of the useful propertiesfat-trees offer. These properties include full bisection-bandwidth andinherent fault-tolerance due to the availability of multiple pathsbetween each source destination pair. The initial idea behind fat-treeswas to employ fatter links between nodes, with more available bandwidth,as the tree moves towards the roots of the topology. The fatter linkscan help to avoid congestion in the upper-level switches and thebisection-bandwidth is maintained.

FIG. 3 shows an illustration of a tree topology in a networkenvironment, in accordance with an embodiment. As shown in FIG. 3, oneor more end nodes 201-204 can be connected in a network fabric 200. Thenetwork fabric 200 can be based on a fat-tree topology, which includes aplurality of leaf switches 211-214, and multiple spine switches or rootswitches 231-234. Additionally, the network fabric 200 can include oneor more intermediate switches, such as switches 221-224.

Also as shown in FIG. 3, each of the end nodes 201-204 can be amulti-homed node, i.e., a single node that is connected to two or moreparts of the network fabric 200 through multiple ports. For example, thenode 201 can include the ports H1 and H2, the node 202 can include theports H3 and H4, the node 203 can include the ports H5 and H6, and thenode 204 can include the ports H7 and H8.

Additionally, each switch can have multiple switch ports. For example,the root switch 231 can have the switch ports 1-2, the root switch 232can have the switch ports 3-4, the root switch 233 can have the switchports 5-6, and the root switch 234 can have the switch ports 7-8.

In accordance with an embodiment, the fat-tree routing mechanism is oneof the most popular routing algorithm for IB based fat-tree topologies.The fat-tree routing mechanism is also implemented in the OFED (OpenFabric Enterprise Distribution—a standard software stack for buildingand deploying IB based applications) subnet manager, OpenSM.

The fat-tree routing mechanism aims to generate LFTs that evenly spreadshortest-path routes across the links in the network fabric. Themechanism traverses the fabric in the indexing order and assigns targetLIDs of the end nodes, and thus the corresponding routes, to each switchport. For the end nodes connected to the same leaf switch, the indexingorder can depend on the switch port to which the end node is connected(i.e., port numbering sequence). For each port, the mechanism canmaintain a port usage counter, and can use this port usage counter toselect a least-used port each time a new route is added.

In accordance with an embodiment, in a partitioned subnet, nodes thatare not members of a common partition are not allowed to communicate.Practically, this means that some of the routes assigned by the fat-treerouting algorithm are not used for the user traffic. The problem ariseswhen the fat tree routing mechanism generates LFTs for those routes thesame way it does for the other functional paths. This behavior canresult in degraded balancing on the links, as nodes are routed in theorder of indexing. As routing can be performed oblivious to thepartitions, fat-tree routed subnets, in general, provide poor isolationamong partitions.

In accordance with an embodiment, a Fat-Tree is a hierarchical networktopology that can scale with the available network resources. Moreover,Fat-Trees are easy to build using commodity switches placed on differentlevels of the hierarchy. Different variations of Fat-Trees are commonlyavailable, including k-ary-n-trees, Extended Generalized Fat-Trees(XGFTs), Parallel Ports Generalized Fat-Trees (PGFTs) and Real LifeFat-Trees (RLFTs).

A k-ary-n-tree is an n level Fat-Tree with k^(n) end nodes and n·k^(n−1)switches, each with 2 k ports. Each switch has an equal number of up anddown connections in the tree. XGFT Fat-Tree extends k-ary-n-trees byallowing both different number of up and down connections for theswitches, and different number of connections at each level in the tree.The PGFT definition further broadens the XGFT topologies and permitsmultiple connections between switches. A large variety of topologies canbe defined using XGFTs and PGFTs. However, for practical purposes, RLFT,which is a restricted version of PGFT, is introduced to define Fat-Treescommonly found in today's HPC clusters. An RLFT uses the same port-countswitches at all levels in the Fat-Tree.

Input/Output (I/O) virtualization

In accordance with an embodiment, I/O Virtualization (IOV) can provideavailability of I/O by allowing virtual machines (VMs) to access theunderlying physical resources. The combination of storage traffic andinter-server communication impose an increased load that may overwhelmthe I/O resources of a single server, leading to backlogs and idleprocessors as they are waiting for data. With the increase in number ofI/O requests, IOV can provide availability; and can improve performance,scalability and flexibility of the (virtualized) I/O resources to matchthe level of performance seen in modern CPU virtualization.

In accordance with an embodiment, IOV is desired as it can allow sharingof I/O resources and provide protected access to the resources from theVMs. IOV decouples a logical device, which is exposed to a VM, from itsphysical implementation. Currently, there can be different types of IOVtechnologies, such as emulation, paravirtualization, direct assignment(DA), and single root-I/O virtualization (SR-IOV).

In accordance with an embodiment, one type of IOV technology is softwareemulation. Software emulation can allow for a decoupledfront-end/back-end software architecture. The front-end can be a devicedriver placed in the VM, communicating with the back-end implemented bya hypervisor to provide I/O access. The physical device sharing ratio ishigh and live migrations of VMs are possible with just a fewmilliseconds of network downtime. However, software emulation introducesadditional, undesired computational overhead.

In accordance with an embodiment, another type of IOV technology isdirect device assignment. Direct device assignment involves a couplingof I/O devices to VMs, with no device sharing between VMs. Directassignment, or device passthrough, provides near to native performancewith minimum overhead. The physical device bypasses the hypervisor andis directly attached to the VM. However, a downside of such directdevice assignment is limited scalability, as there is no sharing amongvirtual machines—one physical network card is coupled with one VM.

In accordance with an embodiment, Single Root IOV (SR-IOV) can allow aphysical device to appear through hardware virtualization as multipleindependent lightweight instances of the same device. These instancescan be assigned to VMs as passthrough devices, and accessed as VirtualFunctions (VFs). The hypervisor accesses the device through a unique(per device), fully featured Physical Function (PF). SR-IOV eases thescalability issue of pure direct assignment. However, a problempresented by SR-IOV is that it can impair VM migration. Among these IOVtechnologies, SR-IOV can extend the PCI Express (PCIe) specificationwith the means to allow direct access to a single physical device frommultiple VMs while maintaining near to native performance. Thus, SR-IOVcan provide good performance and scalability.

SR-IOV allows a PCIe device to expose multiple virtual devices that canbe shared between multiple guests by allocating one virtual device toeach guest. Each SR-IOV device has at least one physical function (PF)and one or more associated virtual functions (VF). A PF is a normal PCIefunction controlled by the virtual machine monitor (VMM), or hypervisor,whereas a VF is a light-weight PCIe function. Each VF has its own baseaddress (BAR) and is assigned with a unique requester ID that enablesI/O memory management unit (IOMMU) to differentiate between the trafficstreams to/from different VFs. The IOMMU also apply memory and interrupttranslations between the PF and the VFs.

Unfortunately, however, direct device assignment techniques pose abarrier for cloud providers in situations where transparent livemigration of virtual machines is desired for data center optimization.The essence of live migration is that the memory contents of a VM arecopied to a remote hypervisor. Then the VM is paused at the sourcehypervisor, and the VM's operation is resumed at the destination. Whenusing software emulation methods, the network interfaces are virtual sotheir internal states are stored into the memory and get copied as well.Thus the downtime could be brought down to a few milliseconds.

However, migration becomes more difficult when direct device assignmenttechniques, such as SR-IOV, are used. In such situations, a completeinternal state of the network interface cannot be copied as it is tiedto the hardware. The SR-IOV VFs assigned to a VM are instead detached,the live migration will run, and a new VF will be attached at thedestination. In the case of InfiniBand and SR-IOV, this process canintroduce downtime in the order of seconds. Moreover, in an SR-IOVshared port model the addresses of the VM will change after themigration, causing additional overhead in the SM and a negative impacton the performance of the underlying network fabric.

InfiniBand SR-IOV Architecture—Shared Port

There can be different types of SR-IOV models, e.g. a shared port model,a virtual switch model, and a virtual port model.

FIG. 4 shows an exemplary shared port architecture, in accordance withan embodiment. As depicted in the figure, a host 300 (e.g., a hostchannel adapter) can interact with a hypervisor 310, which can assignthe various virtual functions 330, 340, 350, to a number of virtualmachines. As well, the physical function can be handled by thehypervisor 310.

In accordance with an embodiment, when using a shared port architecture,such as that depicted in FIG. 4, the host, e.g., HCA, appears as asingle port in the network with a single shared LID and shared QueuePair (QP) space between the physical function 320 and the virtualfunctions 330, 350, 350. However, each function (i.e., physical functionand virtual functions) can have their own GID.

As shown in FIG. 4, in accordance with an embodiment, different GIDs canbe assigned to the virtual functions and the physical function, and thespecial queue pairs, QP0 and QP1 (i.e., special purpose queue pairs thatare used for InfiniBand management packets), are owned by the physicalfunction. These QPs are exposed to the VFs as well, but the VFs are notallowed to use QP0 (all SMPs coming from VFs towards QP0 are discarded),and QP1 can act as a proxy of the actual QP1 owned by the PF.

In accordance with an embodiment, the shared port architecture can allowfor highly scalable data centers that are not limited by the number ofVMs (which attach to the network by being assigned to the virtualfunctions), as the LID space is only consumed by physical machines andswitches in the network.

However, a shortcoming of the shared port architecture is the inabilityto provide transparent live migration, hindering the potential forflexible VM placement. As each LID is associated with a specifichypervisor, and shared among all VMs residing on the hypervisor, amigrating VM (i.e., a virtual machine migrating to a destinationhypervisor) has to have its LID changed to the LID of the destinationhypervisor. Furthermore, as a consequence of the restricted QP0 access,a subnet manager cannot run inside a VM.

InfiniBand SR-IOV Architecture Models—Virtual Switch (vSwitch)

FIG. 5 shows an exemplary vSwitch architecture, in accordance with anembodiment. As depicted in the figure, a host 400 (e.g., a host channeladapter) can interact with a hypervisor 410, which can assign thevarious virtual functions 430, 440, 450, to a number of virtualmachines. As well, the physical function can be handled by thehypervisor 410. A virtual switch 415 can also be handled by thehypervisor 401.

In accordance with an embodiment, in a vSwitch architecture each virtualfunction 430, 440, 450 is a complete virtual Host Channel Adapter(vHCA), meaning that the VM assigned to a VF is assigned a complete setof IB addresses (e.g., GID, GUID, LID) and a dedicated QP space in thehardware. For the rest of the network and the SM, the HCA 400 looks likea switch, via the virtual switch 415, with additional nodes connected toit. The hypervisor 410 can use the PF 420, and the VMs (attached to thevirtual functions) use the VFs.

In accordance with an embodiment, a vSwitch architecture providetransparent virtualization. However, because each virtual function isassigned a unique LID, the number of available LIDs gets consumedrapidly. As well, with many LID addresses in use (i.e., one each foreach physical function and each virtual function), more communicationpaths have to be computed by the SM and more Subnet Management Packets(SMPs) have to be sent to the switches in order to update their LFTs.For example, the computation of the communication paths might takeseveral minutes in large networks. Because LID space is limited to 49151unicast LIDs, and as each VM (via a VF), physical node, and switchoccupies one LID each, the number of physical nodes and switches in thenetwork limits the number of active VMs, and vice versa.

InfiniBand SR-IOV Architecture Models—Virtual Port (vPort)

FIG. 6 shows an exemplary vPort concept, in accordance with anembodiment. As depicted in the figure, a host 300 (e.g., a host channeladapter) can interact with a hypervisor 410, which can assign thevarious virtual functions 330, 340, 350, to a number of virtualmachines. As well, the physical function can be handled by thehypervisor 310.

In accordance with an embodiment, the vPort concept is loosely definedin order to give freedom of implementation to vendors (e.g. thedefinition does not rule that the implementation has to be SRIOVspecific), and a goal of the vPort is to standardize the way VMs arehandled in subnets. Wth the vPort concept, both SR-IOV Shared-Port-likeand vSwitch-like architectures or a combination of both, that can bemore scalable in both the space and performance domains, can be defined.A vPort supports optional LIDs, and unlike the Shared-Port, the SM isaware of all the vPorts available in a subnet even if a vPort is notusing a dedicated LID.

InfiniBand SR-IOV Architecture Models—vSwitch with Prepopulated LIDs

In accordance with an embodiment, the present disclosure provides asystem and method for providing a vSwitch architecture with prepopulatedLIDs.

FIG. 7 shows an exemplary vSwitch architecture with prepopulated LIDs,in accordance with an embodiment. As depicted in the figure, a number ofswitches 501-504 can provide communication within the network switchedenvironment 600 (e.g., an IB subnet) between members of a fabric, suchas an InfiniBand fabric. The fabric can include a number of hardwaredevices, such as host channel adapters 510, 520, 530. Each of the hostchannel adapters 510, 520, 530, can in turn interact with a hypervisor511, 521, and 531, respectively. Each hypervisor can, in turn, inconjunction with the host channel adapter it interacts with, setup andassign a number of virtual functions 514, 515, 516, 524, 525, 526, 534,535, 536, to a number of virtual machines. For example, virtual machine1 550 can be assigned by the hypervisor 511 to virtual function 1 514.Hypervisor 511 can additionally assign virtual machine 2 551 to virtualfunction 2 515, and virtual machine 3 552 to virtual function 3 516.Hypervisor 531 can, in turn, assign virtual machine 4 553 to virtualfunction 1 534. The hypervisors can access the host channel adaptersthrough a fully featured physical function 513, 523, 533, on each of thehost channel adapters.

In accordance with an embodiment, each of the switches 501-504 cancomprise a number of ports (not shown), which are used in setting alinear forwarding table in order to direct traffic within the networkswitched environment 600.

In accordance with an embodiment, the virtual switches 512, 522, and532, can be handled by their respective hypervisors 511, 521, 531. Insuch a vSwitch architecture each virtual function is a complete virtualHost Channel Adapter (vHCA), meaning that the VM assigned to a VF isassigned a complete set of IB addresses (e.g., GID, GUID, LID) and adedicated QP space in the hardware. For the rest of the network and theSM (not shown), the HCAs 510, 520, and 530 look like a switch, via thevirtual switches, with additional nodes connected to them.

In accordance with an embodiment, the present disclosure provides asystem and method for providing a vSwitch architecture with prepopulatedLIDs. Referring to FIG. 5, the LIDs are prepopulated to the variousphysical functions 513, 523, 533, as well as the virtual functions514-516, 524-526, 534-536 (even those virtual functions not currentlyassociated with an active virtual machine). For example, physicalfunction 513 is prepopulated with LID 1, while virtual function 1 534 isprepopulated with LID 10. The LIDs are prepopulated in an SR-IOVvSwitch-enabled subnet when the network is booted. Even when not all ofthe VFs are occupied by VMs in the network, the populated VFs areassigned with a LID as shown in FIG. 5.

In accordance with an embodiment, much like physical host channeladapters can have more than one port (two ports are common forredundancy), virtual HCAs can also be represented with two ports and beconnected via one, two or more virtual switches to the external IBsubnet.

In accordance with an embodiment, in a vSwitch architecture withprepopulated LIDs, each hypervisor can consume one LID for itselfthrough the PF and one more LID for each additional VF. The sum of allthe VFs available in all hypervisors in an IB subnet, gives the maximumamount of VMs that are allowed to run in the subnet. For example, in anIB subnet with 16 virtual functions per hypervisor in the subnet, theneach hypervisor consumes 17 LIDs (one LID for each of the 16 virtualfunctions plus one LID for the physical function) in the subnet. In suchan IB subnet, the theoretical hypervisor limit for a single subnet isruled by the number of available unicast LIDs and is: 2891 (49151available LIDs divided by 17 LIDs per hypervisor), and the total numberof VMs (i.e., the limit) is 46256 (2891 hypervisors times 16 VFs perhypervisor). (In actuality, these numbers are actually smaller sinceeach switch, router, or dedicated SM node in the IB subnet consumes aLID as well). Note that the vSwitch does not need to occupy anadditional LID as it can share the LID with the PF

In accordance with an embodiment, in a vSwitch architecture withprepopulated LIDs, communication paths are computed for all the LIDs thefirst time the network is booted. When a new VM needs to be started thesystem does not have to add a new LID in the subnet, an action thatwould otherwise cause a complete reconfiguration of the network,including path recalculation, which is the most time consuming part.Instead, an available port for a VM is located (i.e., an availablevirtual function) in one of the hypervisors and the virtual machine isattached to the available virtual function.

In accordance with an embodiment, a vSwitch architecture withprepopulated LIDs also allows for the ability to calculate and usedifferent paths to reach different VMs hosted by the same hypervisor.Essentially, this allows for such subnets and networks to use a LID MaskControl (LMC) like feature to provide alternative paths towards onephysical machine, without being bound by the limitation of the LMC thatrequires the LIDs to be sequential. The freedom to use non-sequentialLIDs is particularly useful when a VM needs to be migrated and carry itsassociated LID to the destination.

In accordance with an embodiment, along with the benefits shown above ofa vSwitch architecture with prepopulated LIDs, certain considerationscan be taken into account. For example, because the LIDs areprepopulated in an SR-IOV vSwitch-enabled subnet when the network isbooted, the initial path computation (e.g., on boot-up) can take longerthan if the LIDs were not pre-populated.

InfiniBand SR-IOV Architecture Models—vSwitch with Dynamic LIDAssignment

In accordance with an embodiment, the present disclosure provides asystem and method for providing a vSwitch architecture with dynamic LIDassignment.

FIG. 8 shows an exemplary vSwitch architecture with dynamic LIDassignment, in accordance with an embodiment. As depicted in the figure,a number of switches 501-504 can provide communication within thenetwork switched environment 700 (e.g., an IB subnet) between members ofa fabric, such as an InfiniBand fabric. The fabric can include a numberof hardware devices, such as host channel adapters 510, 520, 530. Eachof the host channel adapters 510, 520, 530, can in turn interact with ahypervisor 511, 521, 531, respectively. Each hypervisor can, in turn, inconjunction with the host channel adapter it interacts with, setup andassign a number of virtual functions 514, 515, 516, 524, 525, 526, 534,535, 536, to a number of virtual machines. For example, virtual machine1 550 can be assigned by the hypervisor 511 to virtual function 1 514.Hypervisor 511 can additionally assign virtual machine 2 551 to virtualfunction 2 515, and virtual machine 3 552 to virtual function 3 516.Hypervisor 531 can, in turn, assign virtual machine 4 553 to virtualfunction 1 534. The hypervisors can access the host channel adaptersthrough a fully featured physical function 513, 523, 533, on each of thehost channel adapters.

In accordance with an embodiment, each of the switches 501-504 cancomprise a number of ports (not shown), which are used in setting alinear forwarding table in order to direct traffic within the networkswitched environment 700.

In accordance with an embodiment, the virtual switches 512, 522, and532, can be handled by their respective hypervisors 511, 521, 531. Insuch a vSwitch architecture each virtual function is a complete virtualHost Channel Adapter (vHCA), meaning that the VM assigned to a VF isassigned a complete set of IB addresses (e.g., GID, GUID, LID) and adedicated QP space in the hardware. For the rest of the network and theSM (not shown), the HCAs 510, 520, and 530 look like a switch, via thevirtual switches, with additional nodes connected to them.

In accordance with an embodiment, the present disclosure provides asystem and method for providing a vSwitch architecture with dynamic LIDassignment. Referring to FIG. 7, the LIDs are dynamically assigned tothe various physical functions 513, 523, 533, with physical function 513receiving LID 1, physical function 523 receiving LID 2, and physicalfunction 533 receiving LID 3. Those virtual functions that areassociated with an active virtual machine can also receive a dynamicallyassigned LID. For example, because virtual machine 1 550 is active andassociated with virtual function 1 514, virtual function 514 can beassigned LID 5. Likewise, virtual function 2 515, virtual function 3516, and virtual function 1 534 are each associated with an activevirtual function. Because of this, these virtual functions are assignedLIDs, with LID 7 being assigned to virtual function 2 515, LID 11 beingassigned to virtual function 3 516, and LID 9 being assigned to virtualfunction 1 534. Unlike vSwitch with prepopulated LIDs, those virtualfunctions not currently associated with an active virtual machine do notreceive a LID assignment.

In accordance with an embodiment, with the dynamic LID assignment, theinitial path computation can be substantially reduced. When the networkis booting for the first time and no VMs are present then a relativelysmall number of LIDs can be used for the initial path calculation andLFT distribution.

In accordance with an embodiment, much like physical host channeladapters can have more than one port (two ports are common forredundancy), virtual HCAs can also be represented with two ports and beconnected via one, two or more virtual switches to the external IBsubnet.

In accordance with an embodiment, when a new VM is created in a systemutilizing vSwitch with dynamic LID assignment, a free VM slot is foundin order to decide on which hypervisor to boot the newly added VM, and aunique non-used unicast LID is found as well. However, there are noknown paths in the network and the LFTs of the switches for handling thenewly added LID. Computing a new set of paths in order to handle thenewly added VM is not desirable in a dynamic environment where severalVMs may be booted every minute. In large IB subnets, computing a new setof routes can take several minutes, and this procedure would have torepeat each time a new VM is booted.

Advantageously, in accordance with an embodiment, because all the VFs ina hypervisor share the same uplink with the PF, there is no need tocompute a new set of routes. It is only needed to iterate through theLFTs of all the physical switches in the network, copy the forwardingport from the LID entry that belongs to the PF of the hypervisor—wherethe VM is created—to the newly added LID, and send a single SMP toupdate the corresponding LFT block of the particular switch. Thus thesystem and method avoids the need to compute a new set of routes.

In accordance with an embodiment, the LIDs assigned in the vSwitch withdynamic LID assignment architecture do not have to be sequential. Whencomparing the LIDs assigned on VMs on each hypervisor in vSwitch withprepopulated LIDs versus vSwitch with dynamic LID assignment, it isnotable that the LIDs assigned in the dynamic LID assignmentarchitecture are non-sequential, while those prepopulated in aresequential in nature. In the vSwitch dynamic LID assignmentarchitecture, when a new VM is created, the next available LID is usedthroughout the lifetime of the VM. Conversely, in a vSwitch withprepopulated LIDs, each VM inherits the LID that is already assigned tothe corresponding VF, and in a network without live migrations, VMsconsecutively attached to a given VF get the same LID.

In accordance with an embodiment, the vSwitch with dynamic LIDassignment architecture can resolve the drawbacks of the vSwitch withprepopulated LIDs architecture model at a cost of some additionalnetwork and runtime SM overhead. Each time a VM is created, the LFTs ofthe physical switches in the subnet are updated with the newly added LIDassociated with the created VM. One subnet management packet (SMP) perswitch is needed to be sent for this operation. The LMC-likefunctionality is also not available, because each VM is using the samepath as its host hypervisor. However, there is no limitation on thetotal amount of VFs present in all hypervisors, and the number of VFsmay exceed that of the unicast LID limit. Of course, not all of the VFsare allowed to be attached on active VMs simultaneously if this is thecase, but having more spare hypervisors and VFs adds flexibility fordisaster recovery and optimization of fragmented networks when operatingclose to the unicast LID limit.

InfiniBand SR-IOV Architecture Models—vSwitch with Dynamic LIDAssignment and Prepopulated LIDs

FIG. 9 shows an exemplary vSwitch architecture with vSwitch with dynamicLID assignment and prepopulated LIDs, in accordance with an embodiment.As depicted in the figure, a number of switches 501-504 can providecommunication within the network switched environment 800 (e.g., an IBsubnet) between members of a fabric, such as an InfiniBand fabric. Thefabric can include a number of hardware devices, such as host channeladapters 510, 520, 530. Each of the host channel adapters 510, 520, 530,can in turn interact with a hypervisor 511, 521, and 531, respectively.Each hypervisor can, in turn, in conjunction with the host channeladapter it interacts with, setup and assign a number of virtualfunctions 514, 515, 516, 524, 525, 526, 534, 535, 536, to a number ofvirtual machines. For example, virtual machine 1 550 can be assigned bythe hypervisor 511 to virtual function 1 514. Hypervisor 511 canadditionally assign virtual machine 2 551 to virtual function 2 515.Hypervisor 521 can assign virtual machine 3 552 to virtual function 3526. Hypervisor 531 can, in turn, assign virtual machine 4 553 tovirtual function 2 535. The hypervisors can access the host channeladapters through a fully featured physical function 513, 523, 533, oneach of the host channel adapters.

In accordance with an embodiment, each of the switches 501-504 cancomprise a number of ports (not shown), which are used in setting alinear forwarding table in order to direct traffic within the networkswitched environment 800.

In accordance with an embodiment, the virtual switches 512, 522, and532, can be handled by their respective hypervisors 511, 521, 531. Insuch a vSwitch architecture each virtual function is a complete virtualHost Channel Adapter (vHCA), meaning that the VM assigned to a VF isassigned a complete set of IB addresses (e.g., GID, GUID, LID) and adedicated QP space in the hardware. For the rest of the network and theSM (not shown), the HCAs 510, 520, and 530 look like a switch, via thevirtual switches, with additional nodes connected to them.

In accordance with an embodiment, the present disclosure provides asystem and method for providing a hybrid vSwitch architecture withdynamic LID assignment and prepopulated LIDs. Referring to FIG. 7,hypervisor 511 can be arranged with vSwitch with prepopulated LIDsarchitecture, while hypervisor 521 can be arranged with vSwitch withprepopulated LIDs and dynamic LID assignment. Hypervisor 531 can bearranged with vSwitch with dynamic LID assignment. Thus, the physicalfunction 513 and virtual functions 514-516 have their LIDs prepopulated(i.e., even those virtual functions not attached to an active virtualmachine are assigned a LID). Physical function 523 and virtual function1 524 can have their LIDs prepopulated, while virtual function 2 and 3,525 and 526, have their LIDs dynamically assigned (i.e., virtualfunction 2 525 is available for dynamic LID assignment, and virtualfunction 3 526 has a LID of 11 dynamically assigned as virtual machine 3552 is attached). Finally, the functions (physical function and virtualfunctions) associated with hypervisor 3 531 can have their LIDsdynamically assigned. This results in virtual functions 1 and 3, 534 and536, are available for dynamic LID assignment, while virtual function 2535 has LID of 9 dynamically assigned as virtual machine 4 553 isattached there.

In accordance with an embodiment, such as that depicted in FIG. 8, whereboth vSwitch with prepopulated LIDs and vSwitch with dynamic LIDassignment are utilized (independently or in combination within anygiven hypervisor), the number of prepopulated LIDs per host channeladapter can be defined by a fabric administrator and can be in the rangeof 0<=prepopulated VFs<=Total VFs (per host channel adapter), and theVFs available for dynamic LID assignment can be found by subtracting thenumber of prepopulated VFs from the total number of VFs (per hostchannel adapter).

In accordance with an embodiment, much like physical host channeladapters can have more than one port (two ports are common forredundancy), virtual HCAs can also be represented with two ports and beconnected via one, two or more virtual switches to the external IBsubnet.

InfiniBand—Inter-Subnet Communication (Fabric Manager)

In accordance with an embodiment, in addition to providing an InfiniBandfabric within a single subnet, embodiments of the current disclosure canalso provide for an InfiniBand fabric that spans two or more subnets.

FIG. 10 shows an exemplary multi-subnet InfiniBand fabric, in accordancewith an embodiment. As depicted in the figure, within subnet A 1000, anumber of switches 1001-1004 can provide communication within subnet A1000 (e.g., an IB subnet) between members of a fabric, such as anInfiniBand fabric. The fabric can include a number of hardware devices,such as, for example, channel adapter 1010. Host channel adapter 1010can in turn interact with a hypervisor 1011. The hypervisor can, inturn, in conjunction with the host channel adapter it interacts with,setup a number of virtual functions 1014. The hypervisor canadditionally assign virtual machines to each of the virtual functions,such as virtual machine 1 1015 being assigned to virtual function 11014. The hypervisor can access their associated host channel adaptersthrough a fully featured physical function, such as physical function1013, on each of the host channel adapters. Within subnet B 1040, anumber of switches 1021-1024 can provide communication within subnet B1040 (e.g., an IB subnet) between members of a fabric, such as anInfiniBand fabric. The fabric can include a number of hardware devices,such as, for example, channel adapter 1030. Host channel adapter 1030can in turn interact with a hypervisor 1031. The hypervisor can, inturn, in conjunction with the host channel adapter it interacts with,setup a number of virtual functions 1034. The hypervisor canadditionally assign virtual machines to each of the virtual functions,such as virtual machine 2 1035 being assigned to virtual function 21034. The hypervisor can access their associated host channel adaptersthrough a fully featured physical function, such as physical function1033, on each of the host channel adapters. It is noted that althoughonly one host channel adapter is shown within each subnet (i.e., subnetA and subnet B), it is to be understood that a plurality of host channeladapters, and their corresponding components, can be included withineach subnet.

In accordance with an embodiment, each of the host channel adapters canadditionally be associated with a virtual switch, such as virtual switch1012 and virtual switch 1032, and each HCA can be set up with adifferent architecture model, as discussed above. Although both subnetswithin FIG. 10 are shown as using a vSwitch with prepopulated LIDarchitecture model, this is not meant to imply that all such subnetconfigurations must follow a similar architecture model.

In accordance with an embodiment, at least one switch within each subnetcan be associated with a router, such as switch 1002 within subnet A1000 being associated with router 1005, and switch 1021 within subnet B1040 being associated with router 1006.

In accordance with an embodiment, at least one device (e.g., a switch, anode . . . etc.) can be associated with a fabric manager (not shown).The fabric manager can be used, for example, to discover inter-subnetfabric topology, create a fabric profile (e.g., a virtual machine fabricprofile), build virtual machine related database objects that forms thebasis for building a virtual machine fabric profile. In addition, thefabric manager can define legal inter-subnet connectivity in terms ofwhich subnets are allowed to communicate via which router ports usingwhich partition numbers.

In accordance with an embodiment, when traffic at an originating source,such as virtual machine 1 within subnet A, is addressed to a destinationin a different subnet, such as virtual machine 2 within subnet B, thetraffic can be addressed to the router within subnet A, i.e., router1005, which can then pass the traffic to subnet B via its link withrouter 1006.

Virtual Dual Port Router

In accordance with an embodiment, a dual port router abstraction canprovide a simple way for enabling subnet-to-subnet router functionalityto be defined based on a switch hardware implementation that has theability to do GRH (global route header) to LRH (local route header)conversion in addition to performing normal LRH based switching.

In accordance with an embodiment, a virtual dual-port router canlogically be connected outside a corresponding switch port. This virtualdual-port router can provide an InfiniBand specification compliant viewto a standard management entity, such as a Subnet Manager.

In accordance with an embodiment, a dual-ported router model impliesthat different subnets can be connected in a way where each subnet fullycontrols the forwarding of packets as well as address mappings in theingress path to the subnet, and without impacting the routing andlogical connectivity within either of the incorrectly connected subnets.

In accordance with an embodiment, in a situation involving anincorrectly connected fabric, the use of a virtual dual-port routerabstraction can also allow a management entity, such as a Subnet Managerand IB diagnostic software, to behave correctly in the presence ofun-intended physical connectivity to a remote subnet.

FIG. 11 shows an interconnection between two subnets in a highperformance computing environment, in accordance with an embodiment.Prior to configuration with a virtual dual port router, a switch 1120 insubnet A 1101 can be connected through a switch port 1121 of switch1120, via a physical connection 1110, to a switch 1130 in subnet B 1102,via a switch port 1131 of switch 1130. In such an embodiment, eachswitch port, 1121 and 1131, can act both as switch ports and routerports.

In accordance with an embodiment, a problem with this configuration isthat a management entity, such as a subnet manager in an InfiniBandsubnet, cannot distinguish between a physical port that is both a switchport and a router port. In such a situation, a SM can treat the switchport as having a router port connected to that switch port. But if theswitch port is connected to another subnet, via, for example, a physicallink, with another subnet manager, then the subnet manager can be ableto send a discovery message out on the physical link. However, such adiscovery message cannot be allowed at the other subnet.

FIG. 12 shows an interconnection between two subnets via a dual-portvirtual router configuration in a high performance computingenvironment, in accordance with an embodiment.

In accordance with an embodiment, after configuration, a dual-portvirtual router configuration can be provided such that a subnet managersees a proper end node, signifying an end of the subnet that the subnetmanager is responsible for.

In accordance with an embodiment, at a switch 1220 in subnet A 1201, aswitch port can be connected (i.e., logically connected) to a routerport 1211 in a virtual router 1210 via a virtual link 1223. The virtualrouter 1210 (e.g., a dual-port virtual router), which while shown asbeing external to the switch 1220 can, in embodiments, be logicallycontained within the switch 1220, can also comprise a second routerport, router port II 1212. In accordance with an embodiment, a physicallink 1203, which can have two ends, can connect the subnet A 1201 viafirst end of the physical link with subnet B 1202 via a second end ofthe physical link, via router port II 1212 and router port II 1232,contained in virtual router 1230 in subnet B 1202. Virtual router 1230can additionally comprise router port 1231, which can be connected(i.e., logically connected) to switch port 1241 on switch 1240 via avirtual link 1233.

In accordance with an embodiment, a subnet manager (not shown) on subnetA can detect router port 1211, on virtual router 1210 as an end point ofthe subnet that the subnet manager controls. The dual-port virtualrouter abstraction can allow the subnet manager on subnet A to deal withsubnet A in a usual manner (e.g., as defined per the InfiniBandspecification). At the subnet management agent level, the dual-portvirtual router abstraction can be provided such that the SM sees thenormal switch port, and then at the SMA level, the abstraction thatthere is another port connected to the switch port, and this port is arouter port on a dual-port virtual router. In the local SM, aconventional fabric topology can continue to be used (the SM sees theport as a standard switch port in the topology), and thus the SM seesthe router port as an end port. Physical connection can be made betweentwo switch ports that are also configured as router ports in twodifferent subnets.

In accordance with an embodiment, the dual-port virtual router can alsoresolve the issue that a physical link could be mistakenly connected tosome other switch port in the same subnet, or to a switch port that wasnot intended to provide a connection to another subnet. Therefore, themethods and systems described herein also provide a representation ofwhat is on the outside of a subnet.

In accordance with an embodiment, within a subnet, such as subnet A, alocal SM determines a switch port, and then determines a router portconnected to that switch port (e.g., router port 1211 connected, via avirtual link 1223, to switch port 1221). Because the SM sees the routerport 1211 as the end of the subnet that the SM manages, the SM cannotsend discovery and/or management messages beyond this point (e.g., torouter port II 1212).

In accordance with an embodiment, the dual-port virtual router describedabove provides a benefit that the dual-port virtual router abstractionis entirely managed by a management entity (e.g., SM or SMA) within thesubnet that the dual-port virtual router belongs to. By allowingmanagement solely on the local side, a system does not have to providean external, independent management entity. That is, each side of asubnet to subnet connection can be responsible for configuring its owndual-port virtual router.

In accordance with an embodiment, in a situation where a packet, such asan SMP, is addressed to a remote destination (i.e., outside of the localsubnet) arrives at a local target port that is not configured as a thedual-port virtual router described above, then the local port can returna message specifying that it is not a router port.

Many features of the present invention can be performed in, using, orwith the assistance of hardware, software, firmware, or combinationsthereof. Consequently, features of the present invention may beimplemented using a processing system (e.g., including one or moreprocessors).

FIG. 13 shows a method for supporting dual-port virtual router in a highperformance computing environment, in accordance with an embodiment. Atstep 1310, the method can provide at one or more computers, includingone or more microprocessors, a first subnet, the first subnet comprisinga plurality of switches, the plurality of switches comprising at least aleaf switch, wherein each of the plurality of switches comprise aplurality of switch ports, a plurality of host channel adapters, eachhost channel adapters comprising at least one host channel adapter port,a plurality of end nodes, wherein each of the end nodes are associatedwith at least one host channel adapter of the plurality of host channeladapters, and a subnet manager, the subnet manager running on one of theplurality of switches and the plurality of host channel adapters.

At step 1320, the method can configure a switch port of the plurality ofswitch ports on a switch of the plurality of switches as a router port.

At step 1330, the method can logically connect the switch portconfigured as the router port to a virtual router, the virtual routercomprising at least two virtual router ports.

Router SMA Abstraction in Order to Allow SMP-Based Connectivity Checks

In accordance with an embodiment, a Subnet Management Packet (SMP) isnot allowed to have addressing information that implies that the packetwill be sent beyond router ports. However, in order to allow discoveryof physical connectivity on the remote side of a (virtual) router port(that is, local discovery of remote connectivity), a new set of SMAattributes can be defined, where each such new attribute represents anindication of “remote information” along with either a standard orvendor specific SMA attribute.

In accordance with an embodiment, when a router SMA processes attributesthat represent “remote” information/attributes, then a corresponding SMPrequest can be sent on the external physical link in a way that is fullytransparent to the sender of the original request.

In accordance with an embodiment, a local SMA can chose to performremote discovery independently of incoming requests and then cacherelevant information locally, or it can act like a simple proxy andgenerate a corresponding request to the external link each time itreceives a request specifying “remote” information/attributes.

In accordance with an embodiment, by tracking whether an SMP requestinga “remote” attribute is received from the local subnet side (i.e., thevirtual router port that is logically connected to the local switchport) or from the external link (i.e., the remote side of the virtualrouter), the SMA implementation can track to what extent the remoterequest is valid in terms of either representing the original request inthe local subnet or representing a proxy request from a peer routerport.

In accordance with an embodiment, for an IB specification compliant SM,a router port is an end port in a subnet. Because of this, low-levelSMPs (used to discovery and configure the subnet) cannot be sent acrossa router port. However, in order to maintain routes for inter-subnettraffic, a local SM or fabric manager needs to be able to observe thephysical connectivity on a remote side of a physical link before itmakes any configuration of the local resources. However, in connectionwith this desire to see the remote connectivity, a SM cannot be allowedto configure the remote side of a physical link (that is, a SM'sconfiguration must be contained within its own subnet).

In accordance with an embodiment, SMA model enhancements allow for thepossibility to send a packet (i.e., SMP) that is addressed to a localrouter port. The SMA where the packet is addressed can receive thepacket, and then apply a new attribute that defines that the requestedinformation is on a remote node (e.g., connected by a physical linkacross subnets).

In accordance with an embodiment, the SMA can operate as a proxy(receives an SMP and sends another request), or the SMA can modify theoriginal packet and sent it on as an inter-subnet packet. The SMA canupdate the address information in the packet. This update the additionof a 1-hop direct route path to the SMP. The SMP can then be received bythe remote node (router port). The SMP can work independently of whetheror not the node on the remote end is configured in the same manner(e.g., as a virtual router), or configured as a basic switch port (e.g.,physical connectivity to a legacy switch implementation). Then therequest packet that the receiving node will see is a basic request, andit will respond in the normal way. The fact that the request originatedbeyond the subnet is transparent (invisible) to the receiving node.

In accordance with an embodiment, this allows for remote subnetdiscovery, by a local subnet, by utilizing the abstraction. The providedSMA abstraction allows for the retrieval of information from a remotesubnet (e.g., across a physical link) without the remote side realizingthat it has been queried from the local (i.e., remote to the subnetdiscovery being performed on) subnet.

Addressing Scheme

In accordance with an embodiment, in order to stay compliant with the IBspecification, SMP packets are bound by the boundaries of the subnet(i.e., the SM is not allowed to “see,” or discover information, outsideof the subnet it is associated with). However, there still exists a needto retrieve information, such as connectivity information, from a remoteend of a virtual router port (i.e., one “hop” beyond the subnetboundary). This information can be encoded into a special type of SMP,which can be referred to as a vendor specific SMP (VSMP).

In accordance with an embodiment, a VSMP can generally utilize anaddressing scheme that is similar to a general SMP (subnet bound SMP),both DR (Directed Routing—where an SMP can explicitly indicate whichport it exists from when going from switch to switch) and LID routingcan be used. However, for those attributes that can apply to a remoteend of a router port, a single bit in an attribute modifier can be usedto indicate local port versus remote port. If a remote bit of anattribute is set, then additional handling can occur at the SMArepresenting the router port.

In accordance with an embodiment, an important aspect of the addressingscheme is that the remote peer port of the router port be able torespond to the request, even in case of erroneous configuration orwiring of the system. For instance if the virtual router is connected,via a physical link for example, to a remote subnet at a general switchport of the remote subnet, the SMA handing the general switch port ofthe remote subnet can respond to the request with status valueindicating that the remote attribute is not supported, and the responsecan reach the requesting SM.

In accordance with an embodiment, an SMP (i.e., VSMP) can be sent to alocal router port, either through the use of a DR path or via the LID ofthe router port. If the information requested is for the remote peerport of the router port, then the remote flag/bit of the attributemodifier can be set. When the SMA receives such a VSMP, it can alter thepacket and add an additional DR step addressing the remote end.

In accordance with an embodiment, a portion (e.g., a bit of a 16 bitattribute modifier) of the packet attribute can be used to signalwhether the VSMP is local or remote. For example, by setting thisportion to a value of 1 can imply that the remote peer port is the finaldestination for the VSMP. This portion of the attribute can be referredto as the remote flag.

In accordance with an embodiment, in addition to the remote flag, therecan be additional flags that can indicate which destination instancesthat should process the VSMP along the way to the final destination. Twoadditional portions (e.g., two bits of the attribute modifier) of thepacket attribute can be used for this purpose. A first portion (e.g.,bit 20), referred to as first receiver flag, can indicate that thepacket is expected to be processed when received by the local routerport (which should match the destination address of the originalrequest). When all the expected processing at the first receiver isdone, a second portion (e.g., bit 21 of the attribute modifier) of thepacket attribute can be set and the packet forwarded on to the remoteend. This second portion can be referred to as the second receiver flag.

DR Routed Packet

In accordance with an embodiment, by way of example, a DR routed packetcan follow an exemplary flow. A source node, at LID A, can initiate therequest packet specifying router 1 as the destination node. An exemplaryDR routed packet configuration is here:

-   -   MADHdr.Class=0x81 (DR routed SMP)    -   MADHdr.Method=0x1 (Get)    -   LRH.SLID=LRH.DLID=0xffff (the permissive LID)    -   MADHdr.DrSLID=MADHdr.DrDLID=0xffff    -   MADHdr.AttrlD=<VSMP attrl D>    -   MADHdr.AttrMod.remote=1    -   MADHdr.AttrMod.first_receiver=1    -   MADHdr.lnitPath=DR path to Rtr1 (LID B)    -   MADHdr.HopCnt=N    -   MADHdr.HopPtr=0

When the request packet arrives at router 1, it can be passed on to acorresponding SMA, which can then verify that the request is valid.After verifying the validity of the request, the SMA can then modify thepacket. This modification can include extending the DR path with oneextra hop, and setting the second receiver flag. Such exemplaryconfiguration modification is shown here:

-   -   MADHdr.HopCnt=N+1 (extend the DR path with one extra hop)    -   MADHdr.lnitPath[N+1]=(virtual Router external port number (i.e.        2))    -   MADHdr.AttrMod.second_receiver=1

In accordance with an embodiment, the SMI (subnet management interface)layer of the SMA can update the DR with the extra hop before the SMAforwards the VSMP out on the physical link.

In accordance with an embodiment, for the SMA that receives the VSMP onthe remote side of the physical link, the addressing scheme used by theVSMP can appear to be that of a normally IB defined packet.

In accordance with an embodiment, when the SMA receiving the VSMP on theremote side of the physical link is the VSMP's final destination, theVSMP can be validated by the received SMA. The validation can includechecking input port relative to flag settings. If remote flag and bothfirst and second receive flags are set, then the packet can be receivedon the physical port (i.e., from the external link side of the portconfigured with the virtual router). If remote and only the firstreceiver flag are set, then the packet can arrive on the virtual ink(i.e., from the internal switch side of the virtual router port). If thevalidation fails, then the status can be set to an appropriate errormessage.

FIG. 14 is a flow chart illustrating a DR routed VSMP packet, inaccordance with an embodiment.

At step 1401, in accordance with an embodiment, within subnet A, anentity, such as a subnet manager of subnet A can request, via a DRrouted VSMP, connectivity information. The destination of the DR routedVSMP can be a router within subnet A, such as router 1.

At step 1402, the DR routed VSMP can arrive at router 1. Router 1, in anembodiment and as described above, can be contained in a switch, such asswitch 1. The DR routed VSMP can be passed to the SMA of switch 1 forverification.

At step 1403, in accordance with an embodiment, the SMA can modify theDR routed VSMP. The modification can include extending the hop counter(for the hop across the physical link to the second subnet), and settingthe second receiver flag.

At step 1404, in accordance with an embodiment, the SMI (the SMI beingassociated with the SMA of the switch/router) can update the hop pointerof the VSMP.

At step 1405, in accordance with an embodiment, the SMI can forward theDR VSMP across the subnet boundary between subnet A 1420 and subnet B1430, on a physical link, where a first end of the physical link can beconnected to the router within subnet A, and the second end of thephysical link can be connected to a router within subnet B.

At step 1406, in accordance with an embodiment, SMA′ of the router 2within subnet B 1430 can receive the VSMP from the physical link.

At step 1407, in accordance with an embodiment, SMI′ (associated withSMA′) can validate the VSMP request.

In accordance with an embodiment, the responding entity (e.g., therouter on the remote side of the physical link) can complete the SMPresponse and set a direction attribute indicating a response. Such anexemplary configuration is shown here:

-   -   MADHdr.Method=0x81 (GetResp)    -   MADHdr.Direction=1 (indicating response)

In accordance with an embodiment, the SMI layer can then decrement thehop pointer and forward the response out on the physical link, back tothe local side. The SMA at the local router can revert the modificationsmade on the request. The SMI at the local side router can perform thenormal processing, including decrementing the hop and sending theresponse out on the virtual link to the switch (i.e., on the internalvirtual link between the switch port and the virtual router port). Forthe next hop, the SMI can again decrement the hop and send the packetout on the physical switch port where the request originally arrived.

FIG. 15 is a flow chart illustrating a response to a DR routed VSMPpacket, in accordance with an embodiment.

At step 1501, in accordance with an embodiment, SMA′ of router 2 canfill in the responsive information to the VSMP (e.g., connectivityinformation), and set a directional flag in to indicate a response.

At step 1502, in accordance with an embodiment, SMI′ can decrement thehop pointer of the response and forward the response back from subnet B1530 to subnet A 1520 on, for example, a physical link having two ends.A first end of the physical link can be connected to the router withinsubnet A, and the second end of the physical link can be connected to arouter within subnet B.

At step 1503, in accordance with an embodiment, the SMA at router 1 canreceive the response and revert the modifications done on the VSMP.

At step 1504, in accordance with an embodiment, the SMI at router 1 canprocess the response to the VSMP and send the response on a link (e.g.,virtual link between the virtual router 1 and the physical switch) tothe physical switch.

At step 1505, in accordance with an embodiment, the SMI can decrementthe hop point counter and send the packet out on the physical switchport where the VSMP was originally received.

LID Routed Packet

In accordance with an embodiment, by way of example, a LID routed packetcan follow an exemplary flow. A source node, at LID A, can initiate therequest packet specifying router 1 as the destination node. Such anexemplary packet could have the following configuration:

-   -   MADHdr.Class=0x01 (LID routed SMP)    -   MADHdr.Method=0x1 (Get)    -   LRH.SLID=LID A    -   LRH.DLID=LID B    -   MADHdr.Attrl D=<VSMP attrl D>    -   MADHdr.AttrMod.remote=1    -   MADHdr.AttrMod.first_receiver=1

In accordance with an embodiment, when the request packet arrives atrouter 1, it can be passed on to a corresponding SMA, which can thenverify that the request is valid. After verifying the validity of therequest, the SMA can then modify the packet. This modification caninclude adding a single DR path at the end. Consequently, this meansthat the total address can be a combination of both a LID routed packetand a DR routed hop. An exemplary configuration is here:

-   -   MADHdr.Class=0x81 (DR routed SMP)    -   MADHdr.HopCnt=1    -   MADHdr.HopPtr=0    -   MADHdr.Direction=0 (outbound)    -   MADHdr.lnitPath[1]=(virtual Router external port number (i.e.        2))    -   MADHdr.DrSLID=LRH.SLID (I.e. LRH.SLID contains LID A from the        original requester)    -   MADHdr.DrDLID=0xffff    -   MADHdr.AttrMod.second_receiver=1

In accordance with an embodiment, an SMI layer at the router can processthe outbound packet normally, and send it out on the physical link. Anexemplary configuration is here:

-   -   LRH.SLID=LRH.DLID=0xffff    -   MADHdr.HopPtr=1 (increment by 1)

In accordance with an embodiment, the SMI at the destination router (atthe other end of the physical link) can determine that it is thedestination for the request and pass the VSMP onto the associated SMA.

FIG. 16 is a flow chart illustrating a LID routed VSMP packet, inaccordance with an embodiment.

At step 1601, in accordance with an embodiment, within subnet A, anentity, such as a subnet manager of subnet A can request, via a LIDrouted VSMP, connectivity information. The destination of the LID routedVSMP can be a router within subnet A, such as router 1.

At step 1602, the LID routed VSMP can arrive at router 1. Router 1, inan embodiment and as described above, can be contained in a switch, suchas switch 1. The LID routed VSMP can be passed to the SMA of switch 1for verification.

At step 1603, in accordance with an embodiment, the SMA can modify theDR routed VSMP. The modification can include adding a single hop DRrouted path to the end of the address, extending the hop counter (forthe hop across the physical link to the second subnet), and setting thesecond receiver flag.

At step 1604, in accordance with an embodiment, the SMI (the SMI beingassociated with the SMA of the switch/router) can update the hop pointerof the VSMP.

At step 1605, in accordance with an embodiment, the SMI can forward theoriginally LID routed VSMP across the subnet boundary between subnet A1620 and subnet B 1630, on a physical link, where a first end of thephysical link can be connected to the router within subnet A, and thesecond end of the physical link can be connected to a router withinsubnet B.

At step 1606, in accordance with an embodiment, SMA′ of the router 2within subnet B 1630 can receive the now DR routed VSMP from thephysical link.

At step 1607, in accordance with an embodiment, SMI′ (associated withSMA′) can validate the VSMP request.

In accordance with an embodiment, for a response flow, the SMA at router2 can validate the VSMP. The validation can include checking input portrelative to flag settings. If remote flag and both first and secondreceive flags are set, then the packet can be received on the physicalport (i.e., from the external link side of the port configured with thevirtual router). If remote and only the first receiver flag are set,then the packet can arrive on the virtual ink (i.e., from the internalswitch side of the virtual router port). If the validation fails, thenthe status can be set to an appropriate error message.

In accordance with an embodiment, the SMA′ at router 2 can complete theSMP response and set a direction attribute indicating a response. Suchan exemplary configuration is shown here:

-   -   MADHdr.Method=0x81 (GetResp)    -   MADHdr.Direction=1 (indicating response)    -   LRH.SLID=0xffff    -   LRH.DLID=ReqMAD.MADHdr.SLID=0xffff

The SMI′ at router 2 can then decrement the hop pointer and forward theresponse out on the physical link, back to router 1. The SMA at router 1can then revert the modifications performed on the original request,before forwarding the response out of the physical switch port back tothe source. An exemplary configuration after such reversal is here:

-   -   MADHdr.Class=0x01    -   LRH.DLID=MADHdr.DrSLID (i.e. contains LID A from the original        requester)    -   LRH.SLID=local LID=B

In accordance with an embodiment, the SMA can additionally clear the DRspecific fields of the VSMP so that the response appears to becompletely consistent with the original VSMP when the response arrivesat the original requestor.

In accordance with an embodiment, once the response arrives back at thesource, the source will see a normally router LID response, just as ifit had been processed entirely at router

FIG. 17 is a flow chart illustrating a response to a LID routed VSMPpacket, in accordance with an embodiment.

At step 1701, in accordance with an embodiment, SMA′ of router 2 canfill in the responsive information to the VSMP (e.g., connectivityinformation), and set a directional flag in to indicate a response.

At step 1702, in accordance with an embodiment, SMI′ can decrement thehop pointer of the response and forward the response back from subnet B1730 to subnet A 1720 on, for example, a physical link having two ends.A first end of the physical link can be connected to the router withinsubnet A, and the second end of the physical link can be connected to arouter within subnet B.

At step 1703, in accordance with an embodiment, the SMA at router 1 canreceive the response and revert the modifications done on the VSMP,including taking off the DR routed hop.

At step 1704, in accordance with an embodiment, the SMI at router 1 canprocess the response to the VSMP and send the LID routed response out onthe physical switch port where the VSMP was originally received.

Features of the present invention can be implemented in, using, or withthe assistance of a computer program product which is a storage medium(media) or computer readable medium (media) having instructions storedthereon/in which can be used to program a processing system to performany of the features presented herein. The storage medium can include,but is not limited to, any type of disk including floppy disks, opticaldiscs, DVD, CD-ROMs, microdrive, and magneto-optical disks, ROMs, RAMs,EPROMs, EEPROMs, DRAMs, VRAMs, flash memory devices, magnetic or opticalcards, nanosystems (including molecular memory ICs), or any type ofmedia or device suitable for storing instructions and/or data.

Stored on any one of the machine readable medium (media), features ofthe present invention can be incorporated in software and/or firmwarefor controlling the hardware of a processing system, and for enabling aprocessing system to interact with other mechanism utilizing the resultsof the present invention. Such software or firmware may include, but isnot limited to, application code, device drivers, operating systems andexecution environments/containers.

Features of the invention may also be implemented in hardware using, forexample, hardware components such as application specific integratedcircuits (ASICs). Implementation of the hardware state machine so as toperform the functions described herein will be apparent to personsskilled in the relevant art.

Additionally, the present invention may be conveniently implementedusing one or more conventional general purpose or specialized digitalcomputer, computing device, machine, or microprocessor, including one ormore processors, memory and/or computer readable storage mediaprogrammed according to the teachings of the present disclosure.Appropriate software coding can readily be prepared by skilledprogrammers based on the teachings of the present disclosure, as will beapparent to those skilled in the software art.

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample, and not limitation. It will be apparent to persons skilled inthe relevant art that various changes in form and detail can be madetherein without departing from the spirit and scope of the invention.

The present invention has been described above with the aid offunctional building blocks illustrating the performance of specifiedfunctions and relationships thereof. The boundaries of these functionalbuilding blocks have often been arbitrarily defined herein for theconvenience of the description. Alternate boundaries can be defined solong as the specified functions and relationships thereof areappropriately performed. Any such alternate boundaries are thus withinthe scope and spirit of the invention.

The foregoing description of the present invention has been provided forthe purposes of illustration and description. It is not intended to beexhaustive or to limit the invention to the precise forms disclosed. Thebreadth and scope of the present invention should not be limited by anyof the above-described exemplary embodiments. Many modifications andvariations will be apparent to the practitioner skilled in the art. Themodifications and variations include any relevant combination of thedisclosed features. The embodiments were chosen and described in orderto best explain the principles of the invention and its practicalapplication, thereby enabling others skilled in the art to understandthe invention for various embodiments and with various modificationsthat are suited to the particular use contemplated. It is intended thatthe scope of the invention be defined by the following claims and theirequivalents.

What is claimed is:
 1. A system for supporting SMP-based connectivitychecks across virtual router ports in a high performance computingenvironment, comprising: one or more microprocessors; a first subnet,the first subnet comprising a plurality of switches, the plurality ofswitches comprising at least a leaf switch, wherein each of theplurality of switches comprise a plurality of switch ports, a pluralityof host channel adapters, each host channel adapter comprising at leastone host channel adapter port, a plurality of end nodes, wherein each ofthe end nodes are associated with at least one host channel adapter ofthe plurality of host channel adapters, and a subnet manager, the subnetmanager running on one of the plurality of switches and the plurality ofhost channel adapters; wherein a switch port of the plurality of switchports on a switch of the plurality of switches is configured as a routerport; wherein the switch port configured as the router port is logicallyconnected to a virtual router; wherein the subnet manager sends to theswitch port of the plurality of switch ports on the switch of theplurality of switches configured as the router port a request packetaddressed to the router port, wherein the request packet requestsconnectivity information beyond the router port; and wherein a subnetmanagement agent, residing on the switch of the plurality of switches,modifies the request packet.
 2. The system of claim 1, wherein thevirtual router comprises at least two virtual router ports; and whereinthe switch port configured as the router port is logically connected toa first virtual router port of the at least two virtual router ports. 3.The system of claim 2, wherein the subnet management agent, upon therequest packet being received at the addressed router port, verifiersthe request packet.
 4. The system of claim 3, further comprising: asecond subnet, the second subnet comprising: a plurality of switches ofthe second subnet, the plurality of switches of the second subnetcomprising at least a leaf switch of the second subnet, wherein each ofthe plurality of switches of the second subnet comprise a plurality ofswitch ports of the second subnet, a plurality of host channel adaptersof the second subnet, each host channel adapter of the second subnetcomprising at least one host channel adapter port of the second subnet,a plurality of end nodes of the second subnet, wherein each of the endnodes of the second subnet are associated with at least one host channeladapter of the second subnet of the plurality of host channel adaptersof the second subnet, and a subnet manager of the second subnet, thesubnet manager of the second subnet running on one of the plurality ofswitches of the second subnet and the plurality of host channel adaptersof the second subnet; wherein a switch port of the second subnet of theplurality of switch ports of the second subnet on a switch of theanother plurality of switches of the second subnet is configured as arouter port of the second subnet; wherein the switch port of the secondsubnet configured as the router port of the second subnet is logicallyconnected to a virtual router of the second subnet, the virtual routerof the second subnet comprising at least two virtual router ports of thesecond subnet; and wherein the first subnet is interconnected with thesecond subnet via a physical link.
 5. The system of claim 4, wherein therequest packet is a DR (directed routing) routed packet; and wherein themodification performed by the subnet management agent comprises:extending a hop counter associated with the request by one or more hops;and setting a second receiver flag.
 6. The system of claim 5, wherein asubnet management interface (SMI) associated with the subnet managementagent further modifies the request packet, the modification by the SMIcomprising updating a hop pointer; and wherein the SMI forwards therequest packet to the router port of the second subnet via the physicallink.
 7. The system of claim 4, wherein the request packet is a LIDrouted packet; and wherein the modification performed by the subnetmanagement agent comprises: extending a hop counter associated with therequest by one or more hops; setting a second receiver flag; and addinga one-hope DR routed path to an address of the LID routed packet.
 8. Thesystem of claim 6, wherein a subnet management interface (SMI)associated with the subnet management agent further modifies the requestpacket, the modification by the SMI comprising updating a hop pointer;and wherein the SMI forwards the request packet to the router port ofthe second subnet via the physical link.
 9. A method for supportingSMP-based connectivity checks across virtual router ports in a highperformance computing environment, comprising: providing, at one or morecomputers, including one or more microprocessors, a first subnet, thefirst subnet comprising a plurality of switches, the plurality ofswitches comprising at least a leaf switch, wherein each of theplurality of switches comprise a plurality of switch ports, a pluralityof host channel adapters, each host channel adapter comprising at leastone host channel adapter port, a plurality of end nodes, wherein each ofthe end nodes are associated with at least one host channel adapter ofthe plurality of host channel adapters, and a subnet manager, the subnetmanager running on one of the plurality of switches and the plurality ofhost channel adapters; configuring a switch port of the plurality ofswitch ports on a switch of the plurality of switches as a router portlogically connecting the switch port configured as the router port to avirtual router, the virtual router comprising at least two virtualrouter ports; sending, by the subnet manager, to the switch port of theplurality of switch ports on the switch of the plurality of switchesconfigured as the router port a request packet addressed to the routerport, wherein the request packet requests connectivity informationbeyond the router port; and modifying, by a subnet management agentresiding on the switch of the plurality of switches, the request packet.10. The method of claim 9, wherein the virtual router comprises at leasttwo virtual router ports; and wherein the virtual router comprises atleast two virtual router ports; and wherein the switch port configuredas the router port is logically connected to a first virtual router portof the at least two virtual router ports.
 11. The method of claim 10,wherein the subnet management agent, upon the request packet beingreceived at the addressed router port, verifiers the request packet. 12.The method of claim 11 further comprising: further providing, at the oneor more computers, including the one or more microprocessors, a secondsubnet, the second subnet comprising: a plurality of switches of thesecond subnet, the plurality of switches of the second subnet comprisingat least a leaf switch of the second subnet, wherein each of theplurality of switches of the second subnet comprise a plurality ofswitch ports of the second subnet, a plurality of host channel adaptersof the second subnet, each host channel adapter of the second subnetcomprising at least one host channel adapter port of the second subnet,a plurality of end nodes of the second subnet, wherein each of the endnodes of the second subnet are associated with at least one host channeladapter of the second subnet of the plurality of host channel adaptersof the second subnet, and a subnet manager of the second subnet, thesubnet manager of the second subnet running on one of the plurality ofswitches of the second subnet and the plurality of host channel adaptersof the second subnet; configuring a switch port of the second subnet ofthe plurality of switch ports of the second subnet on a switch of theanother plurality of switches of the second subnet as a router port ofthe second subnet; wherein the switch port of the second subnetconfigured as the router port of the second subnet is logicallyconnected to a virtual router of the second subnet, the virtual routerof the second subnet comprising at least two virtual router ports of thesecond subnet; and wherein the first subnet is interconnected with thesecond subnet via a physical link.
 13. The method of claim 12, whereinthe request packet is a DR (directed routing) routed packet; and whereinthe modification performed by the subnet management agent comprises:extending a hop counter associated with the request by one or more hops;and setting a second receiver flag.
 14. The method of claim 13, whereina subnet management interface (SMI) associated with the subnetmanagement agent further modifies the request packet, the modificationby the SMI comprising updating a hop pointer; and wherein the SMIforwards the request packet to the router port of the second subnet viathe physical link.
 15. The method of claim 12, wherein the requestpacket is a LID routed packet; and wherein the modification performed bythe subnet management agent comprises: extending a hop counterassociated with the request by one or more hops; setting a secondreceiver flag; and adding a one-hope DR routed path to an address of theLID routed packet.
 16. The method of claim 15, wherein a subnetmanagement interface (SMI) associated with the subnet management agentfurther modifies the request packet, the modification by the SMIcomprising updating a hop pointer attribute; and wherein the SMIforwards the request packet to the router port of the second subnet viathe physical link.
 17. A non-transitory computer readable storagemedium, including instructions stored thereon for supporting SMP-basedconnectivity checks across virtual router ports in a high performancecomputing environment, which when read and executed by one or morecomputers cause the one or more computers to perform steps comprising:providing, at one or more computers, including one or moremicroprocessors, a first subnet, the first subnet comprising a pluralityof switches, the plurality of switches comprising at least a leafswitch, wherein each of the plurality of switches comprise a pluralityof switch ports, a plurality of host channel adapters, each host channeladapter comprising at least one host channel adapter port, a pluralityof end nodes, wherein each of the end nodes are associated with at leastone host channel adapter of the plurality of host channel adapters, anda subnet manager, the subnet manager running on one of the plurality ofswitches and the plurality of host channel adapters; configuring aswitch port of the plurality of switch ports on a switch of theplurality of switches as a router port logically connecting the switchport configured as the router port to a virtual router, the virtualrouter comprising at least two virtual router ports; sending, by thesubnet manager, to the switch port of the plurality of switch ports onthe switch of the plurality of switches configured as the router port arequest packet addressed to the router port, wherein the request packetrequests connectivity information beyond the router port; and modifying,by a subnet management agent residing on the switch of the plurality ofswitches, the request packet.
 18. The non-transitory computer readablestorage medium of claim 17, wherein the virtual router comprises atleast two virtual router ports; and wherein the virtual router comprisesat least two virtual router ports; and wherein the switch portconfigured as the router port is logically connected to a first virtualrouter port of the at least two virtual router ports.
 19. Thenon-transitory computer readable storage medium of claim 18, wherein thesubnet management agent, upon the request packet being received at theaddressed router port, verifiers the request packet.
 20. Thenon-transitory computer readable storage medium of claim 19, the stepsfurther comprising: further providing, at the one or more computers,including the one or more microprocessors, a second subnet, the secondsubnet comprising: a plurality of switches of the second subnet, theplurality of switches of the second subnet comprising at least a leafswitch of the second subnet, wherein each of the plurality of switchesof the second subnet comprise a plurality of switch ports of the secondsubnet, a plurality of host channel adapters of the second subnet, eachhost channel adapter of the second subnet comprising at least one hostchannel adapter port of the second subnet, a plurality of end nodes ofthe second subnet, wherein each of the end nodes of the second subnetare associated with at least one host channel adapter of the secondsubnet of the plurality of host channel adapters of the second subnet,and a subnet manager of the second subnet, the subnet manager of thesecond subnet running on one of the plurality of switches of the secondsubnet and the plurality of host channel adapters of the second subnet;configuring a switch port of the second subnet of the plurality ofswitch ports of the second subnet on a switch of the another pluralityof switches of the second subnet as a router port of the second subnet;wherein the switch port of the second subnet configured as the routerport of the second subnet is logically connected to a virtual router ofthe second subnet, the virtual router of the second subnet comprising atleast two virtual router ports of the second subnet; and wherein thefirst subnet is interconnected with the second subnet via a physicallink.